The present application relates to non-planar semiconductor devices and a method of forming the same. More particularly, the present application relates to non-planar semiconductor devices including stacked germanium nanowires located over a notched segment of a bulk substrate and a method of forming the same.
For more than three decades, the continued miniaturization of metal oxide semiconductor field effect transistors (MOSFETs) has driven the worldwide semiconductor industry. Various showstoppers to continued scaling have been predicated for decades, but a history of innovation has sustained Moore's Law in spite of many challenges. However, there are growing signs today that metal oxide semiconductor transistors are beginning to reach their traditional scaling limits. Since it has become increasingly difficult to improve MOSFETs and therefore complementary metal oxide semiconductor (CMOS) performance through continued scaling, further methods for improving performance in addition to scaling have become critical.
The use of non-planar semiconductor devices such as, for example, gate-all-around semiconductor nanowire field effect transistors (FETs) is the next step in the evolution of complementary metal oxide semiconductor (CMOS) devices. Semiconductor nanowire field effect transistors (FETs) can achieve higher drive currents with increasingly smaller dimensions as compared to conventional planar FETs. In its basic form, a semiconductor nanowire FET includes a source, a drain and one or more nanowire channels between the source and the drain. A gate electrode, which wraps around the one or more nanowire channels, regulates electron flow through the nanowire channel between the source and drain.
Germanium is known to have a higher electron and hole mobility than silicon and can be considered as a suitable material for n-type MOSFETs and p-type MOSFETs. Formation of germanium nanowires have been proposed utilizing germanium-on-insulator (GeOI) substrates which are expensive, or by selective growth of germanium in trenches, or by sidewall passivation by polymers in reactive-ion etch systems. Despite these advances, there is a need for providing an alternative method of forming germanium nanowires in a stacked configuration utilizing a bulk substrate.